Common Channel Signalling Systems

CCS uses a common channel for all signalling. 

The signalling protocols that can be used with CCS are:

ISDN - Q931  - BRI (2B+D) and PRI 23/30+D varients,
Q Signalling (QSIG) - based on Q931, often used for propriatory PBX/PBX connections
Digital Networks Private Signalling System (DNPSS) - created by BT prior to ISDN standards, typically used in UK
Signalling System 7 (SS7) - typically used on PSTN, signalling can be undertaken before seizure of circuit, high speed and packet based signalling system.
SIGTRAN - transportation of SS7 signals end-to-end over an VoIP network